1. Field of the Invention
The present invention relates to an apparatus for displaying, for the purpose of observation, physiological signals such as a cardiogram on a monitor screen and, more particularly, to an apparatus for displaying physiological signal waveform together with a back scale to enable the waveform to be observed in a still state.
2. Description of the Related Art
Hitherto, in a so-called critical care unit (CCU) for example, means are provided for enabling continuous monitoring of physiological signals such as cardiographic signals thereby making it possible to effect a suitable treatment in the event of any abnormality occurring in the condition of the patient.
When physiological signals such as cardiographic signals are displayed on the monitor screen of a CRT (cathode ray tube) for the purpose of observation, the continuous waveform of such signals are displayed and, when any abnormal waveform is recognized, the waveform is made still and this still waveform, referred to as "freeze waveform", is output to a recorder which produces a hard copy of the waveform. The recorder prints the freeze waveform together with a back scale formed by cross-sections so as to enable analysis of the abnormal waveform for determining timing and amplitude on the time axis with reference to the back scale.
Thus, in the conventional system, it is necessary to form a hard copy of the freeze waveform in the event that any abnormality is recognized during observation. Thus, the work for finding any abnormality in the waveform is quite laborious and detailed analysis of the waveform cannot be conducted when no recorder is available.